Why does my car jump out of gear?

Stop and think before anything else: a car that jumps out of gear can lose drive at exactly the wrong moment, such as when pulling out or overtaking. If it happens more than once, do not rely on the car until it has been inspected.

The usual causes are wear inside the gearbox, a worn or loose gear linkage, or engine and gearbox mounts that let the assembly move too much. This article sets out how to tell what your car is doing and what the repair route normally looks like.

When does the car jump out of gear?

The timing gives strong clues. Popping out when you lift off the accelerator on a downhill or when slowing is typical of wear on the parts that hold the gear engaged. Popping out under hard acceleration or when the engine torque changes can point to a mount letting the engine shift, which stretches the linkage.

Note the gear involved. Many cars show the fault in third, fourth or fifth first, because those gears see the most use on the road, and it is worth telling the garage.

• On the overrun: often internal wear
• Under hard acceleration: check mounts and linkage
• One gear only: wear on that gear's engagement parts
• Only on bumps: loose linkage or mounts

Is it the gearbox itself or the linkage?

Inside the gearbox, selector forks, collars and the small teeth that lock a gear in place can wear, so the gear no longer stays engaged. That kind of wear needs the box opened up.

Outside, the lever on the floor connects to the gearbox by rods, cables and bushes. When these wear or come loose, the movement you make at the lever does not reach the gearbox accurately, so the gear may be only part-engaged. That can be a cheaper and quicker repair, which is why the linkage is checked early.

Can worn engine mounts make a car jump out of gear?

Yes, in some vehicles. A broken or collapsed mount allows the engine and gearbox to rock when torque is applied or released. That movement can pull on the linkage or on the gearbox's own mechanism enough to knock it out of gear.

Signs include a clunk when you set off or lift off the pedal, and a visible rocking of the engine. A garage can check the mounts on the lift. Replacing a worn mount does not always cure the fault, so inspection of the gearbox and linkage goes alongside it.

What will a garage check and do?

We also look at the clutch, since drag at the clutch can make gears hard to hold. If the cause is outside the gearbox, we can often explain the repair straight away.

If the fault is inside the gearbox, the unit comes out for inspection. Depending on what is worn, repair or replacement might be considered. Cost depends on the vehicle, the parts and the time needed to remove and refit the box, so we will explain the options after inspection.

Should I keep driving it until the garage can look?

It is a judgement call that comes down to risk. If it has happened once, rarely, and you can hold the lever in place with a hand, you may decide to drive a short way to a garage with great care. If it happens repeatedly, in several gears, or on busy roads, stopping is the safer choice.

Do not hold the lever with force as a long-term fix, as it may worsen wear. Never drive on if you cannot keep a gear engaged, or if the car loses drive without warning.